A Li 2 S‐TiS 2 ‐Electrolyte Composite for Stable Li 2 S‐Based Lithium–Sulfur Batteries

Li 2 S is a fully lithiated sulfur‐based cathode with a high theoretical capacity of 1166 mAh g −1 that can be coupled with lithium‐free anodes to develop high‐energy‐density lithium–sulfur batteries. Although various approaches have been pursued to obtain a high‐performance Li 2 S cathode, there are still formidable challenges with it (e.g., low conductivity, high overpotential, and irreversible polysulfide diffusion) and associated fabrication processes (e.g., insufficient Li 2 S, excess electrolyte, and low reversible capacity), which have prevented the realization of high electrochemical utilization and stability. Here, a new cathode design composed of a homogeneous Li 2 S‐TiS 2 ‐electrolyte composite that is prepared by a simple two‐step dry/wet‐mixing process is demonstrated, allowing the liquid electrolyte to wet the powder mixture consisting of insulating Li 2 S and conductive TiS 2 . The close‐contact, three‐phase boundary of this system improves the Li 2 S‐activation efficiency and provides fast redox‐reaction kinetics, enabling the Li 2 S‐TiS 2 ‐electrolyte cathode to attain stable cyclability at C/7 to C/3 rates, superior long‐term cyclability over 500 cycles, and promising high‐rate performance up to 1C rate. More importantly, this improved performance results from a cell design attaining a high Li 2 S loading of 6 mg cm −2 , a high Li 2 S content of 75 wt%, and a low electrolyte/Li 2 S ratio of 6.